Chemical mechanical polishing (CMP) is generally known in the art. For example U.S. Pat. No. 5,177,908 issued to Tuttle in 1993 describes a finishing element for semiconductor wafers, having a face shaped to provide a constant, or nearly constant, surface contact rate to a workpiece such as a semiconductor wafer in order to effect improved planarity of the workpiece. U.S. Pat. No. 5,234,867 issued to Schultz et. al. in 1993 describes an apparatus for planarizing semiconductor wafers which in a preferred form includes a rotatable platen for polishing a surface of the semiconductor wafer and a motor for rotating the platen where a non-circular pad is mounted atop the platen to engage and polish the surface of the semiconductor wafer. Fixed abrasive finishing elements are known for polishing semiconductor layers. An example is WO 98/18159 PCT application by Minnesota Mining and Manufacturing.
An objective of polishing of semiconductor layers is to make the semiconductor layers as nearly perfect as possible. Fixed abrasive finishing pad finishing surfaces can suffer from being overly harsh on a workpiece, causing unwanted scratching or other unwanted surface damage, thus reducing the perfection of the surface. Further, a fixed abrasive finishing pad finishing surface can suffer from having a higher than necessary coefficient of friction when finishing a workpiece. This higher than necessary coefficient of friction can lead to other unwanted surface damage. Further, fixed abrasive finishing pads can have abrasive particles unexpectedly break away from their surface during finishing and these broken away abrasive particles can scratch or damage the workpiece surface. Still further, during finishing a particle can break away from the workpiece surface forming a workpiece abrasive particle which can scratch or damage the workpiece surface. These unwanted effects are particularly important and deleterious to yield when manufacturing electronic wafers which require extremely close tolerances in required planarity and feature sizes. If, however, large amounts of boundary lubricant are used, current confidential evaluations indicate that finishing rates can be slowed more than needed which raises the cost to finish a workpiece.
It is an advantage of this invention to reduce the harshness of fixed abrasive finishing pads on the workpiece surface being finished. It is an advantage of this invention to reduce unwanted scratching or other unwanted surface damage on the workpiece surface during finishing. It is further an advantage of this invention to reduce the coefficient of friction during finishing a workpiece to help reduce unwanted surface damage. It is an object of this invention to reduce unwanted damage to the workpiece surface when during finishing with a fixed abrasive finishing element an abrasive particle unexpectedly breaks away from their surface. It is an advantage of the invention to reduce unwanted damage to the workpiece surface when an abrasive workpiece particle breaks away workpiece surface during finishing. It is further an advantage of this invention to help improve yield for workpieces having extremely close tolerances such as semiconductor wafers. It is further an advantage of this invention to develop a method with improved optimization of finishing rates and boundary lubrication.
These and other advantages of the invention will become readily apparent to those of ordinary skill in the art after reading the following disclosure of the invention.